With respect to stoves and related appliances, various kinds of stoves—electric, gas, smooth cooktop using glass or metal tops—and toaster ovens are well known to be used for heating food. In addition, “mobile stove-type appliances” such as hot plates and warming trays are well known to be used for heating food. Each of these kinds of stoves and “mobile stove-type appliances” present a safety problem since the heating elements of the stove are hot during the cooking process and remain hot well afterwards. During the cooking process, the safety problem caused by touching the heating element is mitigated somewhat by visual inspection of the stove. With a gas, electric or smooth top stove, for example, the presence of a pot or other utensil on top of the stove might alert someone to the fact that the stove appears to be in use for cooking and therefore too hot to touch. Even the presence of a pot or other utensil is not a reliable clue, however, since people tend to leave tea kettles on their stove perpetually. When the cooking process has ended, however, it is generally impossible to detect that the heating elements of the stove remains hot and would burn the skin of anyone who touched them. There is no visual or other clue that the stove is hot.
To some degree, adults have developed an inherent caution when approaching stoves because of their experience and knowledge in dealing with such safety problems. This inherent caution, however, does not obviate the need for a device that warns the adult when touching the stove would be dangerous. Moreover, children, and particularly young children, usually have not developed such a watchfulness and there has long been a need for a device that can prevent burn accidents to children who may inadvertently touch a stove that is hot, especially when the stove remains hot well after the cooking process has ended.
Furthermore, the reduction in the size of modern kitchens has led the occupants of modern apartments to make use of the stove as an extension of the counter top adjacent the stove as a resting places for large items that have been carried into the kitchen area. An example of such items is heavy bags of groceries brought into the kitchen. There is an urge to set the bags down on the nearest flat surfaces, which may be the top of a stove adjacent a counter top. This is particularly true for those stoves that are smooth on top, such as smooth cooktops. In general, the top surfaces of modern kitchen stoves are increasingly flat, especially the top surfaces of smooth cooktops. These factors have only increased the danger to adults when the top surfaces of stoves are used as a resting place for packages, such as groceries brought into the kitchen.
Smooth cooktop stoves presently are also dangerous if touched on their top surface when they are still hot, even after use. These smooth cooktop stoves, or “smoothtops” as they are sometimes called, utilize as the heating element separate areas on the top surface of the stove (at the same location that gas stove would have burners) which are made of glass. Under each area, usually circular, is a strong light source, such as a halogen lights. The light source projects the light upward to the surface area of the smoothtop's heating element—the glass area on the top surface of the stove. Since the glass area is coated on its bottom with a dark coating, when the light strikes it, the heat from the strong light is absorbed by the glass area and these glass surfaces form each heating element of the stove.
Another variation of the smooth cooktop is the use of a “ribbon heating element” where the smooth glass surface is heated by a coiled electric circuit called a “ribbon element” just underneath it instead of by a halogen light source. The heat is transmitted directly upward so that only the heat element itself gets hot and the rest of the cooktop surface remains cool. In some cases, the ribbon heating element also has another feature whereby the heating element is made of two concentric circles so that the option exists of two sizes of the heating element to match the two different sizes of the pans that need to be heated. This new technology does not solve the problem of warning adults and children that the heating element should not be touched when the cooking process has ended. If anything, it generates the additional hazard that someone can be lulled into touching the heating element after thinking the heating element is cool since the surface right adjacent to it is indeed cool.
Some of these problems have been addressed in earlier patents, through use of thermochromic inserts or overlays. Thermochromic materials are those such as some liquid crystals which change color when passing through a given temperature range, and are now familiar from use in inexpensive items, like temperature indicating refrigerator magnets or stick-on aquarium thermometers.
These devices however still suffer from some drawbacks. Flat appliable thermometers tend to be made of plastic, and would melt or be destroyed at the temperatures reached by a kitchen oven. Higher temperature chemical temperature indicating systems are known, such as the semiconductor cadmium sulfide, but must either be included as inserts in original equipment manufacturing, or fired on as a vitreous ceramic. Materials which are both capable of resisting high temperature and are transparent, or which are themselves thermochromic, are brittle, and so unsuitable for forming in thin flat removable displays, which makes it difficult to attach these materials to an existing surface, the way refrigerator magnet thermometer is attachable.
In an additional drawback of the prior art, flat indicators, embedded in or applied to a flat surface, are necessarily only usefully visible through a limited viewing angle. It is readily shown through trigonometry that if an observer is offset an angle α from the vertical or normal to a surface, which offset is also referred to as the angle of incidence, the apparent area of objects on the surface will be reduced by a factor of cos(α): A′ =A cos(α). For example, if an observer is offset 60° from the vertical, i.e., at a 60 degree angle of incidence, viewing a surface from 30° to the surface itself, the apparent size of objects on the surface is reduced by cos(60)=½. For an observer at an angle of incidence of 80° the apparent size has shrunk to less than 18% of the actual size; and at 85° apparent size is less than 9% of actual. An angle of incidence approaching 90° from the vertical is known as a grazing angle. At grazing angles α flat indicator on the surface clearly approaches zero apparent area, and is completely invisible to the observer.
A second problem that arises from looking at something at an angle of the line of sight is specular reflection. Specular or mirror reflection is the reflection of light rays hitting a flat surface with a reflected ray having an angle of incidence equal to that of the incident ray. For most surfaces specular reflectance increases with angle of incidence, so that more ambient light is reflected to a viewer at larger angles of incidence of the line of sight. This effect wipes out the contrast of a display, so that the display cannot be read at large angles, even if the apparent area of the display were otherwise large enough. Depending on the type of materials used, the loss in visibility at a given display angle may be worse than that predicted by apparent area alone. Liquid crystals for example show a contrast with background notably affected by viewing angle, and readability of a liquid crystal display may be degraded at lower angles of incidence than other kinds of display.
In consideration of these two effects, loss of apparent viewing area and increase in specular reflection, flat warning devices are mainly suitable for surfaces usually seen from small angles of incidence. Examples of such surfaces are vertical surfaces near eye-level, like a door of a cabinet mounted oven, or horizontal surfaces significantly below eye-level, like a stove top surface considered in relation to a typical adult height.
However, for a child an ordinary stove top may be near or even above eye level, while small hands can nonetheless reach over the top of a stove to touch dangerously hot surfaces. Similarly, even for an adult some vertical surfaces such as an oven door, may be below eye level, and hence only visible at a large angle of incidence. This would occur while a user is standing at the stove and reaching down to open the oven door. A flat indicator therefore will not be prominent or attention getting in these situations, and may even be invisible to a user.
With respect to toaster ovens, because of the mobility of the unit the danger of touching the window of a toaster oven exceeds that of the typical immobile oven. The toaster oven can be placed on a counter top or other portion of the kitchen not directly in the “cooking center”. Consequently, an adult and especially a child, or the elderly, is not likely to remember not to touch a window of a toaster oven when it is off (soon after it had been on). In addition, the door of a toaster oven can be left open and jut out further toward someone in the kitchen.
Presently, in order to address the danger of touching a hot “smoothtop” stove, such stoves generally have several light indicators, each one corresponding to each heating element, all located in small one rectangular area on the surface of the cooktop. The light indicators remain lit for a certain length of time after the stove's heating element is turned off in order to deter someone from touching the heating element when it is still hot, although “off”. Unfortunately, this attempt to address the danger of touching a hot stove of the smooth cooktop variety is insufficient as a warning system (putting aside the fact that the light indicators are designed only for the smooth cooktop variety stoves to begin with and not for gas and electric coil stoves).
A quick glance at the group of light indicators would not be sufficient to warn the average adult, no less children or the elderly, that a particular heating element is too hot. This is because the group of light indicators do not immediately tell someone which heating elements correspond to which light indicators. At a minimum, several seconds of concentration are needed in order to determine from the light indicators that are “on”, which heating elements are too hot to touch. Many adults, and certainly most children, cannot afford those seconds of deduction since their desire to touch the stove is immediate. In addition, an adult carrying groceries into the kitchen and looking for a counter top to place them on or a child running into and playing in the kitchen are even less likely than the average adult or child to take the time to engage in a several second thinking process. Accordingly, the child or the adult will be inadequately warned about the danger of being burned. With this in mind, it is no surprise that a 1997 industrial design exhibit at the Cooper Hewitt (Smithsonian) in New York demonstrated that over 69% of adults can not match the control knob with its corresponding burner (i.e. heating element) on a stove.
There is also not presently known any effective warning method for the vertical surfaces of oven windows, including the windows of wall ovens, regular ovens and toaster ovens, and especially when such vertical surfaces are not at or near eye level for a user, as mentioned above. This is particularly important since when the oven is turned off, the oven window remains very hot even though it appears that everything is off.
While devices that make use of liquid crystal compositions are known to indicate the surface temperature of an appliance, these devices are not designed to warn someone of the danger of touching hot stoves. For example, U.S. Pat. No. 3,827,301 to Parker discloses an apparatus for indicating the temperature of a surface of an appliance. It has a first portion in contact with the appliance surface or connected by copper wires or heat pipes to the appliance surface. It has a second portion, a poor heat conducting member in heat exchanging relationship to the ambient environment, that has bands of liquid crystal material extending away from the first portion thereby creating a temperature gradient extending away from the surface of the appliance. Devices such as disclosed in Parker that provide temperature determinations are not adequate for instantly warning a child or even an adult that the heating element of a stove is too hot to touch for one thing because quantitative temperature determinations are inadequate to provide the immediate warning that is necessary. Moreover, the device of Parker and other liquid crystal compositions are not specifically suited to be manufactured as part of a stove. In addition, these devices are not suitable as attachments to stoves and certainly not as attachments to a smooth cooktop stove.
The present invention is also applicable, not just to stoves and related appliances, but to any other surface that one may need to be warned that it is hot. There are numerous devices whose surfaces become hot and remain hot even after the device has been shut off either electrically or otherwise. For example, a radiator cap becomes hot and remains hot for a period when the vehicle and radiator are shut off. Also, any kind of piping that is a conduit for hot liquids is an example of a surface that one may need to be warned that it is hot. Other devices having hot surfaces include hot surfaces on fireplace doors, flat irons, chafing dishes, coffee urns, heating pipes, home radiators, glue guns, oven doors, portable heaters of the electric, oil and ceramic disc type, kerosene lamps, kerosene heaters, barbecue grills of the electric, gas or charcoal type, electric woks, electric skillets, deep fryers for home or commercial use, heat lamps in self service cafeterias and salad bars, saunas including the metal box that generates and/or controls the heat, rotisseries, indoor grills whether gas or electric, tea kettles, wood burning stoves, hot electric rollers, hot wax holders used for beauty treatments, bonnet type hair dryers, synthetic braid trimmers, curling irons, portable generators, steam cleaners especially such as in dry cleaning facilities, hot water pipes that are exposed, hot water heaters, furnaces, warming trays, light fixtures such as halogen lamps, popcorn makers (especially commercial ones), toasters, cappuccino and espresso makers, autoclaves used to sterilize instruments in a medical setting, movie projectors and other such hot surfaces. These and other hot surfaces are exposed to children, maintenance works and ordinary adult users.
Accordingly, there is needed a versatile, easily movable and mountable, removably attachable and detachable, and effective, convenient and easy to manufacture device for warning adults, workers and children instantly when any kind of surface, whether it be a stove of any kind or any other surface, is too hot to touch. There is also a need for such a device that is both capable of installation on a previously purchased stove of any known type, including cooktops, electric and gas stoves, and one that is also capable of being manufactured as part of the stove by stove manufacturers. The present invention addresses and satisfies all of these needs and provides other advantages.
There is also a need for an effective, convenient and easy to use, and detachable heat alert safety device that is easily read and understood for warning adults and children when any surface is too hot to touch. Such a device should ideally be positionable at a variety of heights or positions so that it can be custom tailored for children of different height.
Importantly, moreover, there is a need for a heat alert safety device that is versatile enough to be easily positioned on a hot surface and yet be able to be easily removed thereafter when it has served its purpose—either with respect to that surface or it has served its purpose with respect to that particular individual or it has served its purpose for that individual for that particular moment—and then be repositioned elsewhere—either on another hot surface of another object or another surface of the same object or even another portion of the same surface of the same appliance. This is necessary because in order for the heat alert safety device of the present invention to be effective it has to be visible (or at least discernable) and in addition it should be discernable and effective for children, and since children of different ages are of different heights it is advantageous to be able to attach the device to. It is also necessary because a particular individual may decide to relocate the heat alert safety device when a different appliance is used or when a different portion of a kitchen counter is used, or when any other object with a hot surface is activated. It should be noted that by “activated” is included situations when an object is “hot” a certain amount of time after the source of the heat was “on” and it is of course not intended that the device of the present invention is limited to situations when electricity is “on” for an appliance or other object.
In light of the above discussion there is a need for a device which (i) is suitable for temperatures at least up to a high temperature of a gas oven (500° F.) (ii) is capable of conveying information at a grazing angle of sight, relative to the surface the device is mounted on (iii) may be detachably mounted on an existing surface. It is believed that no heretofore known product simultaneously meets these requirements. It would also be advantageous if the device were simple and rugged and could withstand chance mishandling or rough treatment.